Field of the Invention
The present invention relates to a center supporting device for a propeller shaft of a vehicle. More particularly, the present invention relates to a center supporting device for a propeller shaft of a vehicle, which movably supports a stub shaft that connects a front shaft of the propeller shaft with a rear shaft of the propeller shaft and fixes the stub shaft to a vehicle body.
Description of Related Art
A propeller shaft is a shaft that transmits drive power between a transmission (or a transfer case) and a rear differential gear of a four-wheel-drive or rear-wheel-drive vehicle. The propeller shaft may be easily damaged by generation of vibration when increased in length because it is rotated at high speeds while receiving continuous torsion torque and, therefore, utilizes a divided structure. Generally, the propeller shaft is configured using three joints and two tubes.
FIG. 1 is a perspective view illustrating a conventional propeller shaft, and FIG. 2 is a sectional view illustrating a center bearing and bracket assembly mounted to the conventional propeller shaft.
The conventional propeller shaft is located between a transmission (or a transfer case) and a rear differential gear. As illustrated in FIG. 1, the conventional propeller shaft is configured as a structure using three joints and two tubes, which is capable of absorbing movement displacement (variation in length and bending angle of the propeller shaft) caused by movement of the transmission and the rear differential gear during vehicle behavior. The joints are respectively located at an input component 1 coupled to the transmission, an output component 2 coupled to the rear differential gear, and a center component 3 connecting two tubes 4 and 5 to each other.
Each of the input component 1, the output component 2, and the center component 3 has a spline joint structure. The center component 3 is fixed to a vehicle body via a center bearing and bracket assembly 6 and supports the propeller shaft 10 that transmits drive power via rotation thereof.
As illustrated in FIG. 2, the center bearing and bracket assembly 6, which rotatably supports a stub shaft A that connects a front shaft 4 and a rear shaft 5 of the conventional propeller shaft 10 to each other and fixes the stub shaft A to a vehicle body, generally includes a bearing 7, an insulator 8, and a bracket 9. An inner race of the bearing 7 presses and supports the rotating propeller shaft 10. The insulator 8 is located between an outer race of the bearing 7 and the bracket 9 and serves to support the propeller shaft 10, to control displacement behavior of the propeller shaft 10, and to isolate (reduce) vibration (e.g., vibration of a drive system) transmitted from each part to the vehicle body. The bracket 9 is fixed to the vehicle body via, for example, bolts or nuts.
Meanwhile, movement of the transmission and the rear differential gear (rolling of the transmission and pitching of the rear differential gear) may occur at the time of acceleration/deceleration and braking of a vehicle because the transmission and the rear differential gear are formed of an elastic material such as, for example, rubber and flexibly mounted to a vehicle body frame and a sub frame. When the movement is transmitted to the propeller shaft, this may cause large displacement of the propeller shaft.
In addition, movement (e.g., forward/rearward, leftward/rightward, and upward/downward movement) of the propeller shaft may occur according to, for example, traveling conditions, load variation, and road surface conditions.
Accordingly, the propeller shaft essentially requires a structure capable of absorbing various types of movement caused according to traveling conditions.
In the case of the center bearing and bracket assembly that rotatably supports the center component of the propeller shaft and fixes the center component to the vehicle body, the insulator is deformed in proportion to a movement degree of the propeller shaft while the propeller shaft is undergoing the movement as described above because the center bearing is moved along with the propeller shaft, the bracket is fixed to the vehicle body, and the insulator connects the center bearing and the bracket to each other. In addition, the insulator may be assembled in a permanently deformed state according to an initial configuration state (installation angles and installation positions of the transmission and the rear differential gear) regardless of the movement of the propeller shaft.
That is, the insulator functions not only to isolate vibration transmitted from the transmission to the vehicle body through the propeller shaft or vibration generated in the propeller shaft (vibration generated by unbalance of a rotator or joint characteristics), but also to absorb large displacement (variation in length and bending angle of the propeller shaft) caused by movement of the transmission and the differential gear.
Although the rigidity of the insulator between the center bearing and the bracket may be set to be low (soft) in order to maximize vibration isolation, this may cause the insulator to be easily deformed even by low load, thus deteriorating durability. Conversely, when the rigidity of the insulator is set to be high (hard), this may be advantageous for displacement control or durability, but deteriorate vibration isolation performance, thus easily causing Noise, Vibration, and Harshness (NVH) problems. In addition, vibration isolation acts as resistance against variation in length and bending angle of the propeller shaft caused during movement of the transmission and the rear differential gear and, therefore, may cause other side effects.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.